Function serveClientsBlockedOnKeyByModule

src/blocked.cpp:508–549

Helper function for handleClientsBlockedOnKeys(). This function is called * in order to check if we can serve clients blocked by modules using * RM_BlockClientOnKeys(), when the corresponding key was signaled as ready: * our goal here is to call the RedisModuleBlockedClient reply() callback to * see if the key is really able to serve the client, and in that case, * unblock it. */

 * see if the key is really able to serve the client, and in that case,
 * unblock it. */
void serveClientsBlockedOnKeyByModule(readyList *rl) {
    dictEntry *de;

    /* Optimization: If no clients are in type BLOCKED_MODULE,
     * we can skip this loop. */
    if (!g_pserver->blocked_clients_by_type[BLOCKED_MODULE]) return;

    /* We serve clients in the same order they blocked for
     * this key, from the first blocked to the last. */
    de = dictFind(rl->db->blocking_keys,rl->key);
    if (de) {
        list *clients = (list*)dictGetVal(de);
        int numclients = listLength(clients);

        while(numclients--) {
            listNode *clientnode = listFirst(clients);
            client *receiver = (client*)clientnode->value;

            /* Put at the tail, so that at the next call
             * we'll not run into it again: clients here may not be
             * ready to be served, so they'll remain in the list
             * sometimes. We want also be able to skip clients that are
             * not blocked for the MODULE type safely. */
            listRotateHeadToTail(clients);

            if (receiver->btype != BLOCKED_MODULE) continue;

            /* Note that if *this* client cannot be served by this key,
             * it does not mean that another client that is next into the
             * list cannot be served as well: they may be blocked by
             * different modules with different triggers to consider if a key
             * is ready or not. This means we can't exit the loop but need
             * to continue after the first failure. */
            monotime replyTimer;
            elapsedStart(&replyTimer);
            if (!moduleTryServeClientBlockedOnKey(receiver, rl->key)) continue;
            updateStatsOnUnblock(receiver, 0, elapsedUs(replyTimer));

            moduleUnblockClient(receiver);
        }
    }
}

/* This function should be called by Redis every time a single command,
 * a MULTI/EXEC block, or a Lua script, terminated its execution after